Oscillation generator of the arc type



May 5, 1925. 1,537,021

H. C. RENTSCHLER OSCILLATION GENERATOR OF THE ARC TYPE Filed Nov. 9, 1918 WITNESSES; INVENTOR Patented May 5, 1925.

UNITED STATES PATENT OFFICE".

HARVEY C. BENTSCHLER, OF WILK INSIBURG, PENNSYLVANIA, ASSIGNOB, BY HESNE ASSIGNMENTS, TO WESTINGHOUSE LAMP COMPANY, A CORPORATION 01 PENN- sxnvma. v

OSCILLATION GENERATOR OF THE ABC TYPE.

Application filed November 9, 1918. Serial no. 281,910.

To all wlwm it may concern:

Be it known that I, HARVEY C. RENTSCH- LER, a citizen of the United States, and a resident of VVilkinsburg 'in the county of 6 Allegheny and State of lennsylvania, lave invented a new and useful Improvement in Oscillation Generators of the Arc Type, of

which the following is a specification.

My invention relates to alternating-cur-- rent generators ofthe oscillation-arc type, and it has for its object to provide apparatus of the character designated that shall be simple and inexpensive in construction and highly effective in operation.

The single figure of the accompanying drawing is a diagrammatic view of an oscillator. embodyin a preferred form of my invention, toget or with the associated" circuits.

Oscillators of the Duddell and Poulsen type, are well known, wherein a vaporizing arc is maintained between carbon electrodes or between a copper electrode and a carbon electrode in an atmosphere of hydro-carbon z vapor, the are being shunted by a resonant circuit and being continuously blown out by magnetic means.

Apparatus of this character is highly effective in operation but, for certain classes 30 of application, as for small portable outfits, it is somewhat cumbersome and expensive. V

I find that, if a discharge is initiated between refractory metal electrodes, such, for example, as tungsten, within atmospheres of special character, it will cause satisfactory Y oscillations without the necessity for artificial cooling and without the necessity of a magnetic blowout. While some of the claims and descriptive mater in the present application refer to the discharge of an arc, an attempt will also be made to point out the invention with respect to a possible theory of operation involving certain distinctions between the various types of arcs, which willonow be explained. In the arc, as originally understood, the luminous discharge was known to depend upon the character of the disintegrated or vaporized electrode material. This was amply proved and made use of In spectrum analysis. The electrical and illuminating properties of the arc of the present invention are of an entirely different character. The disintegration or evaporation of the elec trode material is of secondary importance, so that the spectrum lines of the glow discharge or glowing arc, as the dischar of the present invention may be rightly called,

are substantial] due only to the properties of the atmosp ere artificially interposed. The roperties, electrical and otherwlse, of the e ectrode material at high incandescence act, in this case, as mere masking effects only of superposable character. The two types of discharge, viz, the old vaporizing arc and.

the new glowing arc, for scientific and engineering purposes are, therefore, to be very carefully distinguished, one from the other. I have found the following facts concerning arcs between refractory electrodes in a mixture of gas with mercury vapor. The mercury vapor in all cases was present only due to the heat from the electrodes vaporizing some of the mercury. The mercury was originally used for simplicity of starting, but the following peculiarities were found and form the basis for my application.

When the gas used was helium with mercury vapor, the arc in all cases was difii'use between the electrodes spreading over both anode and cathode, and the voltagecurrent V characteristic was rather flat.

When usinghydrogen with mercury vapor, the arc could very easily be made to take the form of a fine stream of luminousdischarge between the electrodes, concentrating on both the anode and cathode..-

cross-section.

line discharge could not be brought about and again, if no mercury vapor was present, it was again ver difficult to produce this fine stream disc large. The are voltagecurrent characteristic is very much steeper when operating with this fine stream effect than when operating otherwise and also very much steeper than with any other gases tried. The oscillating arc is much easier to operate, high frequencies are much more readily produced under this condition and unless the fine-stream discharge was present, very high frequencies were impossible. Other details of my-invention will be here inafter more fully set forth.

\ Referring to the drawing for a more detailed understanding of my invention, I show a closed container at 2, formed of glass or other heat-resistant insulating material, this container being mounted for movement into either a vertical or a horizontal position, as by being attached to the end of a pivoted arm 8. For large-capacity apparatus, a. metal container may be employed, suitable insulationbeing provided for the electrodes. The container 2 is provided with a relatively large metallic electrode 4 and with a relatively small metallic electrode 5 mounted in close proximity thereto, these electrodes being formed preferably of tungsten, although other highly refractory metals, such as molybdenum,

zirconium or chromium may be substituted therefor. The electrode 5 should preferably comprise a head of refractory material carried on the end of a wire of smaller The container 2 is further provided with a starting electrode 6, formed preferably of mercury.

A source of unidirectional current is connected through suitable mains 7 and a positive side of the circuit and the smaller electrode 5 is connected to the negative side thereof.

A resonant circuit, embodying an inductive reactor 9 and acapacitive reactor 10, is connected across the leads of the electrodes 4 and, 5 and further includes the primary winding 11 of a transformer 12, the secondary of which is connected to a consumption circuit, such as an antenna 13; although the arc may be inserted directly in the antenna circuit, as is usual in the art, if desired.

Having thus described the arrangement of apparatus embodying my invention, the oporation thereof is as follows. The tube 2 is first swung into the upright or full-line position and the switch 8 is thrown to its upper position. The tube is then agitated until the mercury ofthe electrode 6 splashes into contact with the electrode 5, initiating a small mercury are. This are is permitted to run until the electrode 5 is heated to incan descence, whereupon the switch 8v is thrown to its downward position, and the tube is swung to the horizontal or dotted-line position. The incandescent electrode 5 initially ionizes the gap between the electrodes 4 and 5 and a directcurrent arc flows between these electrodes upon throwing the switch 8, the large electrode 4 being the anode. When running in this manner, the small electrode, operating as the cathode, remains at incandescence, whereas the anode 4, because of its relatively large size, remains comparatively cool. I have shown my tube 2 mounted for movement into either a vertical or a horizontal position so that the mercury may be brought near enough to the electrode5 to be easily splashed thereagainst for starting but may be moved out of the immediate vicinity of the are between the electrodes 45 to vary the relati e proportion of mercury vapor with respect to the hydrogen gas present in the tube, by preventing excessive vaporization of the mercury during normal operation.

It is now found that, by proper adjust ment of the resonant circuit, oscillations of any desired frequency may be produced, as inthe ordinary Duddell or Poulsen are, these oscillations being transferred to the antenna circuit.

Various gases may be placed within the container 2 but I find that very good results may be obtained by the use of hydrogengas considerably under atmospheric pressure as, for example, with an absolute pressure of 40 centimeters of mercury. It should be distinctly understood, however, that I am not restricted to hydrogen as a filling material, as satisfactory results may be secured for audible frequencies with some other gases such, for example, as helium, although the latter has not been found satisfactory for radio frequencies. Furthermore, great latitude in the absolute pressure within the container is possible.

It is well known that an arc starts with considerable difiiculty in a hydrogen atmosphere, and particular attention is directed to the fact that, by starting with an auxiliary mercury vapor arc, as shown, the hydrogen gas is temporarily displaced in the neighborhood of the fixed electrodes, thus permitting a far more ready start than would otherwise be possible. The characteristic of an arc of good oscillating qualities is that, as far as possible, it shall occur as a fine discharge stream. Since hydrogen,

the instantaneous value by reason of its being diatomic, provides a medium for inelastic encounters, any electrons taking devious paths in passingfrom electrode to electrode will experience a considerable slowing up when meeting with the hydrogen, and, therefore, act as ineffectual carriers of the electric discharge. The electrons occurring in the straight-line path between electrodes will, from this point of view, furnish by far the major portion of the current flow. It is this observation, moreover, that explains why gases providing elastic as against inelast1c encounters would not give the finer discharge stream best found with hydrogen.

In another respect, apparatus constructed in accordance with my invention differs in its operating characteristics from the Poulsen and Duddell vaporizing arcs. As is pointed out by Zenneck on pages 233 to 239, inclusive, of Wireless telegraphy (Seelig translation, 1915), the arc generators of the prior art have three conditions of operation, namely, wherein the supplfy o the output current at all times; wherein the instantaneous value of the output current at times excoeds the input current without relighting or reverse current in the arc; and similar action with relighting in the arc.

Obviously, operation of the first-mentioned character is desirable, .asit involves current flow at all times through the arc in the same direction, thus giving rise to a persistent arc. Zenneck states that operation of this type is of no practical importance because of the low energy that may be developed thereby.

Inextension or possible contradiction of these conclusions of Zenneck, I find that operation of the first t pe is entirely feasible with apparatus of t e character above set forth. I am able to transform ample amounts of energy for commercial requirements while maintaining the maximum oscillation current below the supply current, whereby an extremely persistent glowing arc is produced, since the current therein never reverses indirection. While I do not wish to be confined to any specific theory of operation in explanation of these novel results, they appear to flow part1 from the nature of the electrodes employe and partly from the nature of the atmosphere.

I have shown the electrodes 4 and 5 of dissimilar size in order to clearly visualize the fact that they should preferably attain different operating temperatures but, ohviously, these electrodes might well have the same superficial dimensions, if provided with dissimilar heat-radiating means, and attain the identical result. Furthermore, satisfactory operation may be secured with the two electrodes at the same temperature.

It is usually assumed that inductance and current exceeds resistance should be inserted in the supply leads of a loulsen arc generator for proper operation thereof but I have secured successful operation with the use of only a small protective resistor in the supply lead, inductance either being nonessential or being supplied in proper measure by the inherent properties of the supply leads.

While I have shown my'invention in but a single form, it will be obvious to those skilled in the art that it'is susceptible of various minor changes and modifications without departing from the spirit thereof,

and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by theprior art or are specifically set forth in the appended claims.

I claim as my invention: 1. An oscillator comprising an are between solid electrodes in an atmosphere of a mixture of hydrogen and mercury vapor at a. relatively high pressure, whereby a finestream discharge 1s secured.

2. An oscillator comprisin an envelope containing hydrogen at a su stantial pressure anda quantity of mercury vapor, a pair of solid electrodes therein and means for impressing current therebetween, whereby a fine-stream discharge is obtained.

3. A high-frequency electrical oscillator comprising an evacuated sealed envelope containing refractory, closely-spaced electrodes connected to a source of electrical energy, a mixture of hydrogen and mercury vapor in said envelope whereby a fine-line discharge having a relatively-steep voltagecurrent. characteristic occurs between said electrodes and a resonant circuit associated with said electrodes.

4. A high-frequency electrical oscillator comprising an evacuated sealed envelope containing refractory, closely-spaced electrodes connected to a source of direct current, hydrogen at a substantial pressure in said envelope, a quantity of mercury therein, means for starting an are between the mercury and an electrode and means for transferring the are from the mercury to the other electrode, whereby a fine-stream discharge is secured therebetween.

5. A high-frequency electrical oscillator comprising an evacuated sealed envelope containing closely-spaced refractory electrodes in an atmosphere of hydrogen at a pressure of about 40 centimenters of mercury, a quantity of mercury therein, means for'starting an arc with the mercury as the cathode and an electrode as the anode and means for transferring the are from the mercury to the other electrode with a change of the first electrode from an anode to a cathode.

6. A high-frequency electrical oscillator comprising an evacuated sealed envelope enclosing closely-spaced refractory electrodes in an atmosphere of hydrogen at a substancury from the arc and a resonant circuit in tint pressure, a quantity of mercury in said S unt with the are.

envelope, means for starting an are between In testimony whereof, I have hereunto 10 the mercury and an electrode, means for scri ed my name this 1st day of N0v., transferring the are from the mercury to 1918.

the other electrode, means for moving the envelope to change the distance of the mer- HARVEY C. RENTSCHLER. 

